You add "given the circumstances" to a sentence when there are problems with something that make it difficult. When you're making a decision about it, you want to consider those problems. So if you're judging how good something was, "given the circumstances" means that you don't want to use a really strict standard for judging it.
For example, if you and your wife are trying to save up money but only one of you works, you can say:
I think we're doing pretty well given the circumstances.
This means that you aren't saving a lot of money, but you are saving a lot for a couple with only one income.
"Given the circumstances" can come at the beginning of a sentence or at the end.